Low temperature, ambient curable coating compositions are desirable in many applications. For example, such coating compositions are, in at least some cases, preferable over, for example, thermally-cured or radiation cured coating compositions because (i) little or no energy is required to cure the composition, (ii) the materials from which some substrates are constructed cannot withstand elevated temperature cure conditions, and/or (iii) large or complex articles to be coated may not be convenient for processing through thermal or radiation cure equipment. For example, it is often necessary to employ low temperature, ambient curable coating compositions in automotive refinish applications where cure ovens and radiation cure equipment are often not available.
Some low temperature curable coating compositions are based on the hydrolysis and condensation of silane based materials that form a crosslinked Si—O—Si matrix. These compositions often form hard, highly crosslinked films, which are limited in flexibility. Therefore, the resultant coatings are often susceptible to chipping or thermal cracking due to embrittlement of the coating film. As a result, such coatings have not historically been suitable for use in automotive applications, such as automotive refinish applications.
In the automotive industry, by way of example, it is desirable to extend the life of vehicle bodies by protecting them from, for example, the abrasive chipping action of road dirt and debris, such as sand and gravel, that may cause an aesthetically unpleasing chipping of the vehicle body surface, which may also lead to rusting. Often, coating compositions designed to aid in various properties, such as corrosion resistance and chip resistance are employed to protect against such damage.
As a result, it would be desirable to provide low temperature, ambient curable coating compositions, preferably free of isocyanates and low in volatile organic content, which are capable of producing a flexible and/or impact resistant coating when applied to a substrate and cured. Moreover, it would be desirable to provide such coating compositions that are, in at least some cases, suitable for use as a topcoat on a vehicle, such as an automobile, truck, bus, van, boat, or aerospace vehicle, among others.